DTC P0171: System Too Lean (Bank 1); DTC P0172: System Too Rich (Bank 1): Procedure

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
5. Read the DTCs.

   Result

   Result	Proceed to
   DTC P0171 or P0172 is output	A
   DTC P0171 or P0172 and other DTCs are output	B

   HINT: 

   If any DTCs other than P0171 or P0172 are output, troubleshoot those DTCs first.

B → See step   23 

A: Go to next step 

1. Inspect the PCV hose connections. Refer to ON-VEHICLE INSPECTION - Step 2

   OK

   PCV hose is connected correctly and is not damaged.

NG → REPAIR OR REPLACE PCV HOSE 

OK: Go to next step 

1. Check the intake system for vacuum leaks. Refer to ON-VEHICLE INSPECTION .

   OK

   No leaks in intake system.

NG → REPAIR OR REPLACE INTAKE SYSTEM 

OK: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Put the engine in inspection mode (maintenance mode). Refer to INSPECTION MODE PROCEDURE
5. Start the engine.
6. Warm up the engine and run the engine at an engine speed of 2500 rpm for approximately 90 seconds.

   HINT: 

   During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, warm up the engine after charging control has completed.

7. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume / Gas AF Control / AFS Voltage B1S1 and O2S B1S2.
8. Perform the Control the Injection Volume operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).
9. Monitor the voltage outputs of the air fuel ratio sensor and the heated oxygen sensor (AFS Voltage B1S1 and O2S B1S2) displayed on the Techstream.

   HINT: 

   • Change the fuel injection volume within the range of -12% to +12%. The injection volume can be changed in fine gradations.
   • The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.
   • If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

   Standard

   Techstream Display (Sensor)	Injection Volume	Status	Voltage
   AFS Voltage B1S1 (Air fuel ratio)	+12%	Rich	Below 3.1 V
   	-12%	Lean	Higher than 3.4 V
   O2S B1S2 (Heated oxygen)	+12%	Rich	Higher than 0.55 V
   	-12%	Lean	Below 0.4 V

   RESULT
   
   

   Status AFS Voltage B1S1	Status O2S B1S2	Air Fuel Ratio Condition and Air Fuel Ratio Sensor Condition	Suspected Trouble Area	Proceed to
   Lean/Rich	Lean/Rich	Normal	-	A
   Lean	Lean	Actual air fuel ratio lean	PCV valve and hose PCV hose connections Fuel injector assembly blockage Gas leak from exhaust system Intake system Fuel pressure Mass air flow meter sub-assembly Engine coolant temperature sensor EGR valve assembly	A
   Rich	Rich	Actual air fuel ratio rich	Fuel injector assembly leak or blockage Gas leak from exhaust system Ignition system Fuel pressure Mass air flow meter sub-assembly Engine coolant temperature sensor	A
   Lean	Lean/Rich	Air fuel ratio sensor malfunction	Air fuel ratio sensor EGR valve assembly	B
   Rich	Lean/Rich	Air fuel ratio sensor malfunction	Air fuel ratio sensor	B

   • Lean: During Control the Injection Volume, the air fuel ratio sensor output voltage (AFS Voltage B1S1) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S B1S2) is consistently below 0.4 V.
   • Rich: During Control the Injection Volume, the AFS Voltage B1S1 is consistently below 3.1 V, and the O2S B1S2 is consistently higher than 0.55 V.
   • Lean/Rich: During Control the Injection Volume of the Active Test, the output voltage of the heated oxygen sensor alternates correctly.

   HINT: 

   Refer to "Data List / Active Test" [AFS Voltage B1S1 and O2S B1S2]. Refer to DATA LIST / ACTIVE TEST .

B → See step   11 

A: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine and ECT / Data List / Primary / Coolant Temp.
5. Read the Data List twice, when the engine is both cold and warmed up.

   Standard value

   With cold engine: Same as ambient air temperature.

   With warm engine: Between 75°C to 100°C (167°F to 212°F).

NG → See step   24 

OK: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Put the engine in inspection mode (maintenance mode). Refer to INSPECTION MODE PROCEDURE .
5. Start the engine.
6. Enter the following menus: Powertrain / Engine and ECT / Data List / Primary / MAF and Coolant Temp.
7. Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.
8. Read MAF with the engine speed at 2500 rpm.

   Standard

   Between 4.5 gm/sec and 8.5 gm/sec (shift position: P).

   HINT: 

   During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, read the Data List after charging control has completed.

NG → See step   18 

OK: Go to next step 

1. Check the fuel pressure. Refer to ON-VEHICLE INSPECTION - Step 2 .

NG → REPAIR OR REPLACE FUEL SYSTEM 

OK: Go to next step 

1. Check for exhaust gas leaks.

   OK

   No gas leaks

NG → REPAIR OR REPLACE EXHAUST SYSTEM 

OK: Go to next step 

1. Perform a spark test. Refer to ON-VEHICLE INSPECTION - Step 1 .

   HINT: 

   • If the result of the spark test is normal, proceed to the next step.
   • If the spark plugs or ignition system malfunctions, engine misfire may occur. The misfire count can be read using the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Gas Misfire / Cylinder #1 Misfire Count (to Cylinder #4 Misfire Count).

NEXT: Go to next step 

1. Check the injection and volume. Refer to INSPECTION

OK → See step   15 

NG → See step   25 

NG → See step   26 

OK: Go to next step 

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR FUEL RATIO SENSOR - EFI MAIN RELAY) 

OK: Go to next step 

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Replace the air fuel ratio sensor. Refer to REMOVAL .

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Clear the DTCs. Refer to DTC CHECK / CLEAR .
5. Turn the power switch off and wait for at least 30 seconds.
6. Turn the power switch on (IG) and turn the Techstream on.
7. Put the engine in inspection mode (maintenance mode). Refer to INSPECTION MODE PROCEDURE .
8. Start the power and warm it up.
9. Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
10. Enter the following menus: Powertrain / Engine and ECT / Utility / Trouble Codes / Pending.
11. Read the pending DTCs.

    Result

    Result	Proceed to
    DTC P0171 or P0172 is output	A
    DTC is not output	B

B → END 

A: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Put the engine in inspection mode (maintenance mode). Refer to INSPECTION MODE PROCEDURE .
5. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or more.

   HINT: 

   The A/C switch and all accessory switches should be off.

6. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position.
7. Check the engine idling condition and MAP values in the Data List while performing the Active Test.

   HINT: 

   • Do not leave the EGR valve open for 10 seconds or more during the Active Test.
   • Be sure to return the EGR valve to step 0 when the Active Test is completed.
   • Do not open the EGR valve 30 steps or more during the Active Test.

   OK

   MAP and idling condition change in response to EGR step position.

   Standard

   -	EGR Step Position (Active Test)
   	0 Steps	0 to 30 Steps
   Idling condition	Steady idling	Idling changes from steady to rough idling or engine stalls
   MAP (Data List)	MAP value is 20 to 40 kPa (150 to 300 mmHg) (EGR valve is fully closed)	MAP value is at least +10 kPa (75 mmHg) higher than when EGR valve is fully closed

   HINT: 

   During Active Test, if the idling condition does not change in response to EGR step position, then there is probably a malfunction in the EGR valve.

OK → See step   18 

NG → See step   17 

1. Remove the EGR valve assembly. Refer to REMOVAL .
2. Check if the EGR valve is stuck open.

   OK

   EGR valve is tightly closed.

NG → See step   27 

OK: Go to next step 

1. Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter sub-assembly and ECM. Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE .

   HINT: 

   Repair any problems.

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Clear the DTCs. Refer to DTC CHECK / CLEAR .
5. Turn the power switch off and wait for at least 30 seconds.
6. Turn the power switch on (IG) and turn the Techstream on.
7. Put the engine in inspection mode (maintenance mode). Refer to INSPECTION MODE PROCEDURE .
8. Start the engine and warm it up.
9. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
10. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.
11. Read the pending DTCs.
    RESULT
    
    

    Result	Proceed to
    DTC P0171 or P0172 is output	A
    DTC is not output	B

B → END 

A: Go to next step 

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Replace the mass air flow meter sub-assembly. Refer to REMOVAL .

   HINT: 

   If the result of the inspection performed in step 6 indicated no problem, proceed to the next step without replacing the mass air flow meter sub-assembly.

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Clear the DTC. Refer to DTC CHECK / CLEAR .
5. Turn the power switch off and wait for at least 30 seconds.
6. Turn the power switch on (IG) and turn the Techstream on.
7. Put the engine in inspection mode (maintenance mode). Refer to INSPECTION MODE PROCEDURE .
8. Start the engine and warm it up.
9. Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
10. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.
11. Read the pending DTCs.
    RESULT
    
    

    Result	Proceed to
    DTC is not output	A
    DTC P0171 or P0172 is output	B

B → See step   28 

A → END